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What is the aerodynamic drag of an open wheel?
smart51 - 8/12/12 at 05:28 PM

I've trawled google but can't find a figure. Does anyone know what the Cd of an open wheel is?

Dave Ashurst - 8/12/12 at 05:52 PM

I'd guess approx 1.15, on it's own.

The effect overall is more complex - depends on it's position relative to the other parts.

The rear wheel, for example, will be different to the front.

If you contact David Irvine he might be able to model the entire project and calculate a cd for the vehicle.

best
D

Dave Ashurst - 8/12/12 at 05:54 PM

That said, I know that you know what you're doing, so feel free to disregard my ramblings!

smart51 - 8/12/12 at 06:43 PM

Hi Dave,

An infinitely long cylinder has a drag of 1.17. A wheel, being shorter, will be lower, but I'm not sure how much.

It's the sort of thing that I'm sure has been done several times, but Google is perhaps not the place to look because of all the dross.

I know the RWBHP of my trike and the frontal area. As soon as the DVLA permit, I'll find out the top speed, which will give me the overall drag. By estimating the drag of each major part, I can see which bits are best to treat to improve things. I guess wheels are a bit specialist.

phelpsa - 8/12/12 at 07:27 PM

You should find that it depends on how fast it's spinning IIRC.

[Edited on 8-12-12 by phelpsa]

umgrybab - 8/12/12 at 09:43 PM

quote:
Originally posted by phelpsa
You should find that it depends on how fast it's spinning IIRC.

[Edited on 8-12-12 by phelpsa]


I agree, the drag will depend on the speed you are going. The faster the wheel spins, the thinner the boundry layer of the air is. It also depends greatly on the position and size of your front wheel arches.

smart51 - 9/12/12 at 03:48 PM

A bit more digging turned up an example figure of .58 but it depends on the width to diameter ratio and rotation speed.

Simon - 9/12/12 at 11:32 PM

I'd have thought tyre type would have a bearing too - a bald tyre would offer less restance than say a 4x4 tyre.

ATB

Simon